The present invention relates to a radial tire for motorcycles and a method of making the same being capable of improving lateral force variation of the tire.
In the motorcycle, if the lateral force variation of the front tire is large, lateral vibrations occur on the tire and handle-bar, and stability during straight running and cornering is greatly deteriorated. Hitherto, off-center of tire components such as carcass, tread belt and the like caused during building a green tire was regarded as the main cause of lateral force variation. Accordingly, efforts have been made to improve tire uniformity by improving precision of tire components and accuracy in assembling the tire components.
In recent years, the requirements for radial tires for high-performance high-speed motorcycles have become more and more severe. Therefore, to meet such requirements, it becomes necessary to further improve the lateral force variation and the like.
It is therefore, an object of the present invention to provide a radial tire for motorcycles and a method of making the same, in which the lateral force variation is highly improved together with other tire performance.
According to the present invention, a radial tire for motorcycles comprises a carcass extending between bead portions through a tread portion and sidewall portions, and a belt disposed radially outside the carcass in the tread portion and comprising two cross breaker plies of cords laid at angles of from 16 to 26 degrees with respect to the tire equator. And the method of making the radial tire comprises vulcanizing the tire in a mold which causes a variable stretch to the belt during vulcanizing the tire, wherein the stretch at the tire equator is in a range of from 6.0 to 7.0%, and the stretch gradually decreases from the tire equator to the axial edges of the belt. The stretch is defined as (BD2/BD1xe2x88x921)xc3x97100 wherein BD1 is the inside diameter of the belt before tire vulcanization, and BD2 is the inside diameter of the belt during tire vulcanization.